a friend gave me an iphone 4 and has it jailbroke to 6.0 and is unlockable, howe can i revert back to 5.1.1?

You can't get help here. You'll have to ask your "friend".

Give it back.

Hacking an iPhone for any reason is against Apple's license agreement for the iPhone and is not supported by Apple directly or via these discussions.

You'll need to get help from this elsewhere.

There are no supported methods to downgrade the iOS. Use of hacking methods, which can't be discussed here, may cause your phone to be non-upgradable to the released iOS 6

danwhaley79 wrote:

i cannot restore this iphone that someone gave to me, because it has a jailbroke iOS on it, anyone have any suggestions

You can try restoring it using DFU mode. If that fails then you are stuck.

• -Connect the cable to your computer directly, not a hub, and don't connect to the phone yet.
• -Reboot your computer.
• -Disable your antivirus and firewall.
• -Launch iTunes.
• -On the phone, hold the HOME and SLEEP buttons for exactly 10 seconds, until the screen turns black, but before the Apple logo appears. If the logo appears try again.
• -When the screen turns black release the SLEEP button but continue holding the HOME button while you connect the cable to the phone.
• -Wait for iTunes to recognize the phone, then release the HOME button.

If the Restore succeeds you will have a working, non-jailbroken phone. If not, you are out of options we can discuss in an Apple forum.

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